Admiral_Bobski
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Posts posted by Admiral_Bobski
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But this time Pete we have records warmth in Australia (and ongoing drought) to silence their sceptics and a cold U.S./U.K. to throw back at our sceptics. I don't think 97/98 had anything but messed up 'Nino Weather. This Nino' ,and it's warmth, had a lot of competition from factors that cool the planet (the strongest -ve AO recorded?????) and yet still will manange to place the global temps in the top 5. Only a rising baseline temp can have this work in my way of thinking???
We're not still on the "we must still be warming because we have top-5 high temps" argument, are we? I thought we'd gone through this, time and time and time and time and time and time again.
Fluctuations around a baseline occur in dynamic systems - just because the baseline has risen does not necessarily mean that it is rising. There is a difference. I'm not saying that temperatures are not still on the increase, I might add, just that your argument is spurious.
CB
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I think it's important to note that Svante Arrhenius's work is old and predates alot of what is known nowadays about global temperature re-distribution, so although I have a lot of respect for him we have moved on lot, with atmospheric cell placement (i.e hemisphere triple cell, Jet Stream, Ocean conveyors etc).
Hectic, hectic, hectic at the moment, hence my absence, but time for a quick post!
Arrenhius's work is old, granted, but the whole of AGW science stems from his original paper - to the extent that his Greenhouse Gas law is still used to this day (this one: ΔF = α ln(C/C0) ).
The validity, or otherwise, of Arrenhius's paper is one of the fundamental building blocks of the theory of AGW. Although we have come a long way since that paper was written it is still a crucial part of AGW theory. If it is wrong in any way then there may be knock-on effects further down the line.
:huh:
CB
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I'd rather like to know where he says that data were lost as well. Care to help me out, SC?
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This is an interesting question and, especially, answer:
H - If you agree that there were similar periods of warming since 1850 to the current period, and that the MWP is under debate, what factors convince you that recent warming has been largely man-made?
The fact that we can't explain the warming from the 1950s by solar and volcanic forcing - see my answer to your question D.
So at least Dr Jones is compelled by the fact that solar and volcanic forcings can't explain recent trends, which leaves the blame in mankind's lap. By extension, then, if it could be shown that solar effects are, or even could be, responsible for warming then the belief that man is to blame would have to be rescinded, regardless of any other argument.
Hmmm...
CB
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Hi CB,
I'll quickly try to answer 1 and 3 just now, notably the basis for thinking CO2 is important. The effects were predicted well before they were observed, based on the properties of the CO2 molecule in the lab. The range of predictions for sensitivity has actually not really changed since the very first ones early in the 20th Century. Many different recent studies agree that it's very hard to push sensitivity below 1.5C per doubling CO2, but uncertainty exists on how much above. As for the basic greenhouse gas properties- not all atmospheres give you warming: Titan's upper atmosphere exhibits an 'anti-greenhouse effect', where the upper atmosphere is relatively opaque to incoming radiation yet transparent to outgoing longwave radiation leading to net cooling - the reverse of the CO2 greenhouse effect.
http://www.aip.org/h...climate/co2.htm
Very interesting discussion about why you don't need much CO2 to produce warming too.
I'd like to emphasise at this point that I do not (nor have I ever, I think) deny that CO2 is, fundamentally, a GHG, in that it has basic heat trapping properties. My argument, throughout all these years, is that a "dry" experiment in a lab is no comparison with the actual effect of CO2 in the atmosphere, with all of the associated interactions and feedbacks that you get in a massive dynamical system. (By "dry" I mean that it is isolated and small-scale, not that it isn't wet!)
In all fairness, the atmosphere of Titan does still give warming - it just doesn't give as much warming as it would otherwise be expected to:
"The haze containing organic molecules in Titan's upper atmosphere absorb 90% of the solar radiation reaching Titan, but is inefficient at trapping infrared radiation generated by the surface. Although a large greenhouse effect does keep Titan at a much higher temperature than the thermal equilibrium[1], Titan also exhibits an "anti-greenhouse" effect, which partially compensates for the greenhouse warming, and keeps the surface approximately 9°C (16°F) cooler than would otherwise be expected from the greenhouse effect alone[2]. According to McKay et al.,[1] "The anti-greenhouse effect on Titan reduces the surface temperature by 9 K whereas the greenhouse effect increases it by 21 K. The net effect is that the surface temperature (94 K) is 12 K warmer than the effective temperature 82 K. [i.e., the equilibrium that would be reached in the absence of any atmosphere]" (http://en.wikipedia....eenhouse_effect)
In answer to your comment about '3' - you don't need a fancy all-singing all-dancing computer model to do the work. Attribution studies can be done merely on the basis of looking at temperature, ENSO, volcanic, GHG and solar indices and applying regressions, then working out the forcing factors they represent to drive the temperature. Or you can do it by first of all determining the forcing factors for each contributor and then determining the scale of the attribution. There are many definitions of 'model', and not all are unreliable! Android has done the statistical method with ENSO. To be honest, is the LI not another statistical model study, though consciously without CO2 (in that VP needed to tweak factors to get the high correlation?).If you look at your factors as an equation, thus: temp = ENSO+volcanic+GHG+solar,
then your attribution studies are effectively attempting to determine the values of ENSO, volcanic, GHG and solar on the basis that temp is a given.
If we know that temp=10, for example, then we could say that ENSO=1, volcanic=2, GHG=3 and solar=4: that gives us 10. But those attributes are given on the basis of certain assumptions, and not all of those assumptions are entirely objective. It is claimed that GHG effects are well understood, but it is also admitted that solar effects are poorly understood. There is an assumption that GHGs have a greater effect than solar (an assumption based, in part, on the aforementioned "dry" experiments), and so the sun is given a lesser effect than GHGs. But why? We've already admitted that solar effects on climate are poorly understood, so where is the justification for the assumption that solar effects must be less than GHG effects?
The LI is a statistical study, yes. Part of the initial insentive for it was to see whether GHGs were required to replicate 20th century warming. If they are not required then it means one of two things (or maybe both): 1. GHGs have a lesser effect than assumed, and/or 2. statistical analyses of climate are essentially meaningless - the old adage of statistics being able to show anything that you want them to show. If this should be the case then how much can you trust a science based mostly in statistics?
(Which factors are you referring to having been "tweaked" by VP? Just so that we're sure we're on the same page!)
http://www.realclima...enhouse-effect/This one above is quite good, showing:
150W/sq m total greenhouse effect (66-85% water vapour) = 33C warming.
CO2 on it's own contributes 9-26% of this (depending on overlaps in radiative absorption)
Our increase is 3-9%, or 1-2.6C [but without feedbacks or saturation effects - the logarithmic bit - included].
But this is an oversimplification, as they show (but it's a starting point), as water vapour is a feedback, and not a forcing, at least in part demonstrated by the response to volcanic eruptions. But see RealClimate's discussion for more on feedbacks, sensitivity, saturation etc.
http://www.realclima...ack-or-forcing/
And please, I know that RealClimate is maintained by the very people some on here love to hate, but if you're going to dispute anything, dispute the science, not the scientists!
I see little reason to doubt the experimental work giving CO2 it's place as a significant climate driver, and by extension, it's impact on our climate.
sss
Edit: A further thought on LI and Maunder (and I'm prepared to be wrong!) - I see that with low inputs the response could be faster, but to define a cool period, you have to have come down from the previous warm period, where there should be a lag? Right, weekend time, beer o'clock, been some good discussions here!
I haven't had a chance to read up on those links yet - plenty of other things to be reading up on at the moment! - but I will get around to it...promise! I, personally, have no problem with the people who run RealClimate any more. (Well, it would be more accurate to say that I'm not going to go on and on about them any more.) I don't think I've ever refused to read a link on the basis that I don't like or agree with the author - in fact, I was one of the first people on these boards to plead with other posters that we should discuss the science, not the people (and I dropped my argument against Dr Mann at that time - not that I accepted his work, but rather I didn't want to dismiss it on the basis of me not liking its author). So, no point in preaching to the converted!
With regards to the LI and Maunder issue, the point is that there isn't a single time lag, nor are there discrete lag periods in steps - the lag period grows and shrinks continuously with changes in temperature, in a sort of sinusoidal way, making it a bit hard to pin down as "the lag" or even "a lag". I'm trying to find temperature and proxy sunspot data for the period AD800-AD1600 that are granular enough to do a comparative analysis on - I'll keep you posted on that.
CB
EDIT - hope I didn't offend any statisticians back there!
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1) CO2 is a greenhouse gas, as proven many times over in physical experiments, without which Earth would be a much colder place. This has been known for a century.
CO2 is a greenhouse gas - fine. Without it the Earth would be a much colder place...would it? How much colder? Any kind of atmosphere will trap heat to some extent - is the suggestion that the Earth would be "much colder" based upon estimates of CO2's effects which have been derived through AGW theory, or was it determined independently?
2) We have increased significantly the concentration of this, and other, greenhouse gases in the atmosphere, observational evidence.We have increased the concentration, yes. Significantly? Well, the significance of it is dependent upon the effect of these GHGs in the atmosphere which, to my mind, is still open for debate.
3) Observational evidence of global temperature rise steadily since the 1970s, without significant interruption. Departures from the rising trend are readily accounted for by volcanic, ENSO, aerosol and solar irradiance variations.Accounted for by computer models, yes. But accounted for in a 2+2=4 way, or in a 1+3=4 way? Different accounts may be able to reach similar conclusions.
4) Observational evidence confirms that changes are occurring in accordance with the theory: lower tropospheric temp rises, stratospheric cooling, enhanced change at high latitudes, ocean heating, glacier melt, sea ice loss. No other theory predicts this particular pattern of observed changes.Has the tropospheric increase/stratospheric decrease issue been ruled out as being caused by other phenomena? Can the Sun not cause similar warming, as VP has suggested? As for the enhanced change at high latitudes, ocean heating, glacier melt and sea ice loss, these are all symptoms of a warming world - they make no explanation for the cause of that heating. It sounds suspiciously like the argument that "CO2 causes warming: the world is warming - therefore CO2 is responsible for the world warming" - there is no corroboration here, only assumption.
5) Direct observational evidence for a reduction in the quantity of radiation leaving the Earth, which has to equal warming, and crucially it's in the specific wavelengths expected for GHGs.6) Direct observational evidence for increased downward infrared radiation, as expected from an enhanced greenhouse effect.
I have not yet had a chance to read through the links you provided earlier, so I cannot comment on these. I will get back to you once I've had a read
7) Measured sensitivity of Earth's climate to doubling of CO2 by looking at palaeoclimate records - best estimates in the 2C - 4.5C range, but very few lower than 1.5C. We have seen a ~40ppm rise since 1970 (~14% of pre-industrial), and a ~0.5C temperature rise in that time, in line with expectations.[there's more too, like sea level rises consistent with thermal expansion of the oceans, movement of ecological zones]
There is a huge range (relatively) of estimates of climate sensitivity. As I understand it, the IPCC's range of 2-4.5C is the average range from the published research (so some estimates are quite a bit lower and some estimates are quite a bit higher). Determining the climate sensitivity is not an easy task, I grant you, since you have to take into account not just the direct effect of any GHGs, but also the effects of any feedbacks. The uncertainties in our understanding of these feedbacks is going to have a knock-on effect on our understanding of climate sensitivity. A while back I did a back-of-envelope calculation for how the prescribed climate sensitivity range would affect temperatures as CO2 decreases, and those calculations seemed to cause certain contradictions with other established science. I admit that it might be because my calculations are invalid (quite possibly they are) but, as with so many posts on here that use mathematics, the post was largely ignored and no discussion was engaged in. I'll see if I can find the post later on, if I get the chance
It feels like AGW is like the Copernican ideas of a Sun-centred solar system. A really elegant solution to the question that solved all the basic observational problems that plagued early astronomers (retrograde motion, movements of the inner planets etc), and with Galileo's observations and Kepler's mechanics, evidence clearly supported the theory, and the alternatives were needlessly complex (Ptolemaic geocentric system). Not perfect (orbital ellipticities for example, precession dealt with by Newton then Einstein), but a sound understanding of the basic processes. We're at that stage, in that we understand from numerous lines of evidence that a doubling of CO2 leads to between ~2C and ~4.5C as a reasonable estimate, and unlikely to be less than 1.5C. Uncertaintly in some details, but not in the basic process. Any overturning of the theory has to explain the processes and provide alternatives (a la Einstein) for data that does not support the theory, ie the new hypothesis is testable.I don't agree that AGW theory is elegant, at least nothing like as elegant as the Copernican description of the solar system. At times it feels decidedly clunky and awkward. As I have said earlier, I have proposed basic atomic explanations of processes that may occur in the LI, and I am continuing to work on climatological processes in the context of that work. I'd also like to point out that the LI has already made a prediction which was confirmed - in its early stages it predicted the temperature-measurement anomoly around the 1940s. VP and I looked at jigging the figures in an attempt to determine what scale of process would be required to cause that effect, until TWS mentioned that there had been a problem with the data around that time. A quick renormalisation of the data brought the observed temps in line with the LI prediction. Admittedly the LI has come a long way since those heady days(!), but it did make a prediction (postdiction?) which was shown to be about right!
More later
CB
PS - sorry that this post is not in the same scientific league as VP and sss's posts have been, but at least I finally got around to answering sss's questions!
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Can I just quickly ask - when exactly did global warming start?
I always thought it was supposed to be within a few years of the industrial revolution, but these days everyone seems to be saying that it started in the mid-1970s (around the time that the Sun ceases to be a "viable" explanation for it).
And if it was in the mid-1970s then what does it mean to have "excessive" warming over a period of only 30-35 years?
CB
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...but we know that the world has been up to 10C warmer than present in the past, with much more CO2 in the atmosphere.
We also know that it has been as cool as present (if not colder) with a lot more CO2 in the atmosphere, and we know that it has been a lot warmer with as little (or only fractionally more) CO2 in the atmosphere:
CB
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It's worth pointing out that although the studies have shown the total heat content of the oceans continuing to rise, the measurements are down to about 2000m (Argo floats). The average depth of the oceans is 3800m (http://hypertextbook.com/facts/2006/HelenLi.shtml) - that leaves an awful lot of water which could be storing and releasing heat. I think you're right, sss, that this is an area that needs more study and until a complete analysis of the actual total heat content of the oceans is performed the "radiator" question is open to interpretation.
With regards the leaky integrator, I think it is spurious to ask what the mechanism for it is - there could well be various mechanisms all working in concert with one another, the oceans perhaps being just one of them.
CB
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I suspect (don't know, why I'm asking them) that it takes a long time for -ve feedbacks to bring the climate back to an even keel because the big -ve forcings are geological, involving weathering of rocks and the slow biological carbon cycle sinking carbon in the oceans. Thus the PTEM peaked very quickly but had a very long tail - a big slug of CO2 followed by the slow reactions of geology.
Just my guess.
Here's a question for you. You think there might (must?) be big, fast?, -ve feedbacks - right? Any idea what mechanism they/it have/has?
To answer your question, I'm sure there must be some negative feedbacks. Their scale and speed may be a different matter. But the MetO page talks about only two negative feedbcaks, and it talks about both of those tending towards becoming positive - there is no mention of any feedback tending towards negative, on any timescale.
Everything I had read about clouds suggested that they caused a net negative feedback, but new studies are coming out saying that there should be a net positive feedback - I'm a bit skeptical of these studies at the mo' because it just doesn't seem right to me, though I can't quite put my finger on why. It's another area I need to look into, but what with the LI and the (possibly associated) ozone depletion issue I'm a bit swamped right now!
Another potential upcoming negative feedback might (might!) be vulcanism - if the few studies that suggest retreating ice sheets may cause increased seismic activity are correct then there's the potential for a whole bunch of aerosols to be ejected into the atmosphere. What effect this may have in the long term I am not sure, but it's another variable, certainly.
I agree with what sss said earlier about negative feedbacks quite possibly acting more slowly than positive feedbacks, but that introduces new questions like how big those feedbacks must be if they are to override long-established positive influences. It's a complicated area - certainly more complicated than the MetO page makes it appear.
With regards sss's post on the radiator issue:
Provided the total heat content of the oceans is still rising, then the 'radiator' hypothesis should be invalidated? I'm not absolutely certain on the last part, but it makes good sense to me.It does make good sense, but is the total heat content of the ocean rising? Something else for me to double-check!
CB
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I'll ask him, or I'll ask the question via the Met O site to someone as close to him as I can.
Thanks Dev - if you could let us know what he says then I'd be very grateful
Pete, I agree that cyclical factors would flip-flop from positive to negative climate effects, but in terms of actual feedbacks - factors that kick in as a result of some other change - I would have expected there to be at least a few or else the Earth would surely have seen a runaway warming at some point in its long history...?
CB
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Indeed, I would be happy to see Chun Li in space (she's the hot one from Street Fighter
What do you mean Street Fighter isn't real...?)I'd also like to say that I think Dev is making an unnecessarily big deal about the issue of escape velocity - we've been going into space for 60 years...what's the problem?
CB
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Here's a link to the Metoffice article on feedbacks:
http://www.metoffice.gov.uk/climatechange/science/explained/feedbacks.html
Now, according to this, the only negative feedbacks are as follows:
1: the Land Carbon Cycle, which they declare to be "currently negative", suggesting that it is likely to become a positive feedback as warming goes on
2: Clouds, which they say give both positive and negative feedbacks, though as warming goes on the positive overwhelms the negative.
Other than that there are, apparently, no negative feedbacks and not one feedback that is always negative. For a planet that has always maintained some form of equilibrium, that strikes me as being wrong somehow.
CB
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Personally I think that kids (most kids, anyway) are smart enough to realise that what they see in Star Trek and Battlestar Galactica and on their XBox isn't real, and I think they would still be awed by actual live transmissions from the Moon. I remember telling my children about Bush's announcement that they were aiming to land on the Moon by 2020, and they (then aged 9 and 7) were genuinely excited by it - you should have seen their little faces light up at the idea.
I do think that getting commercial interests involved in the space program is a good idea, don't get me wrong, but I think that canning the moon mission is a stunningly bad idea. Getting man to the moon would be hard, but it would be an absolute cinch by comparison to what they overcame in the 60s.
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I still await C-Bob's refute of our culpability for the Ozone hole and it's impacts.
Still? I only posted a couple of days ago!
It's going to take a bit of time to get all the necessary information together, analyse it and see if my hypothesis works, so I wouldn't hold my breath if I were you - could well take a couple of months to even come up with a coherent sketch of the idea.
(And all that intermingled with my far more pressing problems which, hopefully, will be sorted out within the next fortnight
)So, please bear with me and do not adjust your set...
CB
PS - Thanks to Pete and TWS for their kind words.
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D.M. Since I knew it was about time I looked at the places I'm told 'change' will occur first (and most irrefutably) I've been met with a bluster of " Why doesn't Antarctica respond?"
Antarctica has been responding for 20 odd years now but ,because, to the blinkered, things appeared supportive of a B.A.U. world (cold south/warm north = 'balance'!) nothing has been 'pushed'.
Now we know (for sure) that we have helped isolate Antarctica from the worst of the 80's/90's heating should we not worry about the 'Arctic Experience' manifesting itself upon the sea Ice and shelfs remaining over the southern summer?
The Grand Irony of past ,more minor, atmospheric manipulations muting the impacts of accelerated warming over specific regions so as to 'arm' denialists is most titivating.
The ozone hole may have little to nothing to do with CFCs. I've just started working on an alternative explanation which, I think, might tie into the LI. Not sure yet, but guess what the ozone hole (in this theory) is caused by...?
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http://en.wikipedia....-normal_science
Could the whole AGW/GW/CC debate/research/discussion be doing with a bit of this? It looks like an excellent thing to me, a much more "open" and all-encompassing way of making progress.
If we adopted the method here, it might end the constant calling for published papers all the time and the seeming dismissal of anything that has not been published in some scientific journal or other. I have always found that to be particularly annoying.....there is plenty of reliable information available from other sources, it should be used and not dismissed out of hand, as it so often is.
I wish I could find something that I found many years ago. It was something one of the scientists who had to deal with the terrible aftermath of Chernyobl (sp?) said. The above Wiki description just about sums up the approach which he said should have been taken, as opposed to the approach which they had taken.
PS This is not to say that I thought it was a good idea for the IPCC to crib wholly speculative stuff from other publications, such as Rock Climbing Weekly (or whatever it was) and stuff from political extremists groups like Greenpeace. A balance has to be found. I hope I have not come across as contradicting myself, I sometimes have trouble explaining exactly what I mean!
Do I make any sense? Does anyone have any thoughts about Post-normal Science?
I think I'll go and make the tea.......
Interestingly there is a link on that wiki page to a description of Richard Feynman's "Cargo Cult Science", a description which seems to be particularly apt with regards to the way climate science is performed.
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I remember reading, a while ago now, that NASA scientists were investigating the possibility of developing Arthur C. Clarke's old space elevator idea as a means of getting stuff into space without the awkward escape velocity issues. Even without the space elevator, parts could feasibly be flown to the ISS and a ship constructed in space, relatively cheaply and without the need for masses of fuel, which could take men back to the moon or onwards to Mars.
Robots are all very well, in their own way, but nothing is more awe-inspiring, or more productive, than a manned mission. We're rapidly getting to the point, as a species, where we need to start thinking about expansion and colonisation, and Obama's decision is a massive step back for space exploration. I'd rather throw massive amounts of money into the space program than into irresponsible banks (though I am the first to accept -and argue for the fact - that the economic consequences of not bailing out the banks would have been devestating...a tiny part of me thinks that economic collapse may have been just what society needed, though!).
My personal feelings are that, at present, Obama is doing an extremely poor job of leading the West into a bright new future, and his latest decree on the space program is just the latest in a long line of decisions with which I disagree.
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There are so many reasons that we should go back to the moon, not the least of which being that I think this generation really needs the awe-inspiring inspiration of a moon landing.
I forget who it was that said it, but the genral perception seems to be that had we not cancelled the Apollo program in the mid-70s we would almost certainly have had a manned moon base by now from which we could feasibly have already launched manned missions to Mars. A sobering thought.
Those that think space exploration is a waste of money are hopelessly short-sighted, obviously unable to see the benefits for mankind.
After the excitement of the fusion story the other day, Obama's space plans make the most depressing reading...
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There was an article in the paper the other day about water vapour as a major greenhouse gas and I remembered that somewhere on this thread (or the original LI thread) someone (Captain Bobski?) had suggested water vapour but not know how to get figures for it. I would guess you areralready aware of this and if you are interested in it for your LI you'll have looked it up and everything, but I thought it was interesting because it was something I didn't know until I read the LI thread! And the LI is so interesting I thought it would be nice if it didn't drop off the bottom of the page
Gawd bless ya, ma'am! There's nothing like a thread bump every now and again, is there? <_<
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I'm a little horrified to note that I have spelled "decommissioned" with only one "m" twice now, one in each of my last two posts.
What was I thinking?!
I humbly apologise and shall go and hang my head in shame.
One final note - most scientists do not refer to the helium nuclei produced in a fusion reaction as alpha particles. The reason for this is that, even though helium nuclei and alpha particles are absolutely identical, the term "alpha particle" is usually reserved for a particle that is emitted during radioactive decay.
Since, during fusion, the helium nuclei are produced by other atoms being stuck together, they are not considered to be the same thing. Even though they are. Basically. Their energy levels can differ, but that's by the by. It's all a rather strange semantic argument.
Anyway, that's enough from me - I'm supposed to be on Sabbatical!
EDIT - okay, okay! One final final final thing - it appears my physics teacher lied to me...here, apparently, is how smoke detectors work:
"Most smoke detectors contain a small amount of the alpha emitter americium-241. The alpha particles ionize air between a small gap. A small current is passed through that ionized air. Smoke particles from fire that enter the air gap reduce the current flow, sounding the alarm. The isotope is extremely dangerous if inhaled or ingested, but the danger is minimal if the source is kept sealed. Many municipalities have established programs to collect and dispose of old smoke detectors, to keep them out of the general waste stream. "
The principle is the same, though. As the Am241 decays it gives off less and less radiation until it can no longer sufficiently ionise the air to allow a current to reliably pass through it, so your alarm goes off for no apparent reason. You still need a new smoke alarm.
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Just thought I'd post this link: http://edmall.gsfc.n.../ed-fusion.html
I think that the energy-equivalent (E=mC2) of the mass lost in the creation of a Helium nucleus from two Deuterium atoms amounts to gamma radiation? It's a massive amount of MeV!!!
The mass lost does not, as I understand it, come out as gamma radiation but as a high-energy neutron - it's the neutron that contains the energy, and we can harness that energy as the neutron relinquishes it - it's something crazy like 14.1MeV per neutron! In a sustained reaction you're talking about billions of high energy neutrons being created - bear in mind, though, that we can't get all 14.1MeV from every neutron. How much we are able to get from them is what will determine the usefulness of fusion reactors - if we can get more energy out of them than we put in to create them then we have a viable (and cheap!) means of producing energy.
I've just had a trawl around the internet and it seems that a deuterium fusion reaction gives off no gamma radiation whatsoever! Literally all you get is helium nuclei and high energy neutrons. Three things about the neutrons:
1. They are the source of dangerous radioactivity in a fusion reactor - they irradiate the reactor chamber itself, which - as I said earlier - will need to be disposed of carefully during decomissioning.
2. They are the source of the energy that we can harness. It's all a matter of how much we can harness and how efficiently we can do it.
3. They are what make the reaction sustainable. Once the reaction is underway, the high energy neutrons bash into deuterium atoms and cause them to fuse. We should be able to control the reaction by feeding in the fuel (deuterium) at a constant rate - one that's above the sustainability threshold but below the uncontrollable chain-reaction threshold.
So you see, neutrons are our friends.
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Have read the link, Captain. That is what I like........ a positive approach to a looming enegry crisis, rather than a load of hot air from the IPCC.
As I have said ad nauseum....if only the money, time and energy wasted on the promotion of doom and gloom could be put into reearching new forms of energy/power, then it would be a far better use of said resources.
As I am not a nuclear scientist (although I have had two guided tours around the now defunct Oldbury Nuclear Power Station...they liked to have visitors. I know how heavy a spent power rod is as I have held one, they used to let you do all sorts....fascinating! They stopped the guided tours following 9/11. A shame, as it was an excellent and FREE day out!). Anyway, like Ronnie Corbett, I digress. Are there any safety concerns with fusion like there are with fission? Spent waste and stuff like that?
NB I have learned the difference between fission and fusion by reading that link!
Fusion doesn't have anything like the same waste issues as fission does. There are essentially three types of radioactive emissions: alpha particles, beta particles and gamma rays. Alpha particles are essentially helium atom nuclei - only the nuclei because the particles are too energetic to hold onto electrons. Beta particles are high energy electrons (or positrons). Gamma rays are high frequency electromagnetic radiation.
The comparative dangers of these waste products are to do with three factors: their range, their ionisation rate and the number of particles present. The more ionisation they cause, the more dangerous they are to people (they ionise your body at a cellular level, screw up the cell and cause cancer), but the less range they have.
Alpha particles cause extreme ionisation, but they can be stopped very effectively by a sheet of paper. Beta particles cause moderate ionisation and can be stopped by a quite thin sheet of steel. Gamma rays don't cause much ionisation, but they can penetrate several feet of solid lead.
Fission reactions produce a lot of gamma rays. A lot of gamma rays. While an individual quantum (smallest energetic piece, effectively) does not do much damage, gamma rays - like zombies - overwhelm you by sheer numbers. The radiation at Chernobyl, and that which caused so much post-war devestation in Japan, is pretty much entirely gamma radiation.
Fusion reactions, on the other hand, produce very few gamma rays (if any - I must double check that). However, when you squish hydrogen atoms together you actually make helium nuclei - so you're actually making alpha particles, and huge numbers of them at that. Fortunately, an adequately (and easily) shielded reaction chamber can stop these from being a problem. The biggest shielding challenge comes from high energy neutrons, and it is really these that cause some problems further down the line.
Eventually a fusion reactor will need to be decomissioned, and the reaction chamber walls will need to be carefully disposed of because they will be highly radioactive. However, the good news is that the radioactive half-life of this waste is on the order of a few hundred years, which is far, far better than the several thousand year half-lives of fission reaction waste.
Practically speaking, if you were to make a pure fusion bomb (which hasn't been done, I might add - all fusion bombs are two-stage devices which use a fission reaction to trigger the fusion reaction) there would be next to no dangerous nuclear fallout, as opposed to a regular atom bomb (like they dropped on Hiroshima) which causes masses of fallout.
I hope that's helped, noggin (though I've probably only confused you further).
CB
PS - Out of interest, and to give you an idea of the inherent danger of alpha particles, a regular household smoke alarm has a sensor and an alpha particle source inside it - usually Americium 241. The way the alarm works is that the Am241 gives off alpha particles at a regular rate. We know the exact rate at which it decays, so we know exactly how many particles should be detected by the sensor.
When smoke drifts into the alarm, the teeny tiny smoke particles actually stop the alpha particles from making it to the sensor. The sensor doesn't pick up enough particles and that triggers the alarm.
So, smoke alarms work on the principle that alpha particles are very easy to stop!
On a final note, the reason that you need to replace your smoke alarm regularly is that, over time, the Am241 gives off fewer and fewer alpha particles. Eventually a point is reached where it is not emitting enough particles, the sensor is not receiving enough and it triggers the alarm.
If you've ever had a smoke alarm suddenly go off for no very good reason, and over time it does it more and more, then you need to get a new smoke alarm!
And on a final final note, for those interested in pulling a smoke detector apart and seeing what Am241 looks like - DON'T, for God's sake!! Just touching it with your bare skin can be quite bad for you - holding it for any length of time is a supremely bad idea, and if you were to swallow a lump of it then you'd be a numpty.
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Climate - In-depth/technical discussion
in Climate Change
Posted
Hi VP - nice to be back - my head's a bit crowded at the moment so I've not been able to really focus on in-depth technical discussions, but it's starting to clear slightly...!
With regards to Arrhenius's flaws, I've dug up this old PDF which refers to Angstrom's rebuttal of the original Arrhenius paper:
http://docs.lib.noaa.gov/rescue/mwr/029/mwr-029-06-0268a.pdf
In particular is this comment: "The remainder of Angstrom’s paper is devoted to a destructive criticism of the theories put forth by the Swedish chemist, S. Arrhenius, in which the total absorption of CO[2], ie quite inadmissibly inferred from data which include the combined absorption of CO[2], and the vapor of water."
Subsequent to this, Arrhenius's supporters discredited Angstrom's rebuttal (though whether this was valid or not I don't know) by claiming that his experiments were not a legitimate approximation of the actual atmosphere, and that there were errors in the taken measurements.
I'm not sure how those objections invalidate Angstrom's assertion that Arrhenius had not appropriately distinguished between CO2 effects and water vapour effects, so I shall have to do more reading up on the subject - perhaps if I could find Angstrom's actual paper it might help!
CB